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Potassium: Not Too Much, Not Too Little

www.ironmanmagazine.comWhile all minerals are important to health, potassium has special significance for those who exercise. Consider its primary functions in the body: transmission of nerve signals and proper electrical conduction in the heart. Those two features alone make potassium important for any bodybuilding diet.

While potassium is found in most foods, the best sources are fruits and vegetables. Unfortunately, the low-carbohydrate diets followed by many bodybuilders can lead to lower potassium—not just because of the lack of fruits and vegetables but also because low-carb diets produce a natural diuretic effect that causes the excretion of sodium and potassium. In fact, it’s the loss of potassium from very low-carb diets that results in the characteristic fatigue and muscle weakness they often bring. Supplementing with potassium at the right time can make those dietary side effects vanish.

Even so, it has to be at the right time. Taking isolated potassium supplements can lead to the release of the adrenal hormone aldosterone. The human body has evolved to conserve sodium while rapidly eliminating potassium, and that’s what aldosterone does. It retains sodium through its actions in the kidneys while promoting the urinary loss of potassium. In bodybuilders that can cause rapid water retention, requiring them to get more potassium either in food or via a supplement, which should be taken with meals.

Potassium also has a relationship with other minerals. As noted, it works with sodium in controlling fluid in cells. The sodium-potassium-pump mechanism pushes sodium out of cells and potassium into cells, which maintains the proper electrolyte balance in the cells and the blood. In addition, magnesium is needed to retain potassium in cells.

Potassium itself plays a role in helping to restore depleted glycogen after a workout. When you consider that muscle glycogen is the primary fuel of bodybuilding workouts, potassium’s importance becomes clear.

The body has a fine-tuned mechanism to keep potassium within a certain range in the blood. Either too much or too little can lead to serious problems. For example, while having a certain level of potassium is required for the heart to beat, or contract, too much potassium can stop a heart as fast as a bullet. That’s the reason a high-dose of potassium is in the third and final injection of lethal-injection procedures. The first two tranquilize and relax the muscles. The potassium is the actual killer, stopping the heart. Luckily, the body has evolved to prevent a buildup of excess potassium, but it can happen under certain conditions.

As noted, under normal circumstance the body is able to handle larger amounts of potassium. The potassium level is detected in the blood, which then prods the kidneys into collecting and rapidly excreting the excess. Anything that interferes with kidney function can lead to a dangerous buildup of potassium. Having kidney disease, especially kidney failure, is a prime risk factor for potassium overload and such patients are monitored and warned not to take in excess potassium.

Certain drugs can also interfere with kidney function enough to cause potassium retention, including certain blood pressure drugs and potassium-sparing diuretics. The latter encourage the excretion of sodium while retaining potassium in the body. Years ago pro bodybuilder Mike Matarazzo nearly died when he unknowingly took large doses of potassium while using a potassium-sparing diuretic drug shortly before a contest. His goal was to lose excess water, but it easily could have cost him his life.

There are other, less obvious sources of concentrated potassium. A recent medical journal presented two case studies related to excess potassium intake.1 The first case involved a 65-year-old man with heart disease who had been prescribed a low-sodium diet. He began using a salt substitute that contained potassium chloride. He used eight teaspoons a day, sprinkled on his meals, in addition to taking a prescribed potassium supplement. That led to an emergency room visit, in which he complained of breathing difficulty and muscle weakness. He also had a slow heartbeat and low blood pressure. Not long after showing up, he went into respiratory depression; that is, he couldn’t breathe on his own. His blood potassium level was 8.5; the normal range is 3.5 to 5.0. The attending doctors gave him medication to lower his potassium, and he left the hospital 11 days later.

The other patient discussed in the article was a 35-year-old bodybuilder who showed up at the ER suffering from weakness and the inability to move. He showed decreased alertness, a slow heartbeat and low blood pressure. He was immediately given an anesthetic drug, followed by a muscle relaxant. Oddly enough, one of the side effects of the muscle relaxant was elevated blood potassium. Talk about putting oil on a fire! Not surprisingly, he went into cardiac arrest. He was resuscitated and then the standard medical protocol for lowering elevated blood potassium, medication that was formulated to push the excess blood potassium back into cells.

It turns out that the bodybuilder had been taking a lot of potassium to treat muscle pain. On the day he was admitted to the ER, he had taken 10 potassium tablets before training and another 10 after the workout. He had also consumed several sports drinks during the workout that contained about 1,320 milligrams of potassium each. His estimated total potassium intake was 8,000 milligrams, about twice the recommended daily dose.

Bodybuilders can also get elevated blood potassium after incurring severe muscle damage, a process known as rhabdomyolysis that causes potassium from damaged muscle cells to be rapidly released into the blood. Still, there was no indication that this occurred with this bodybuilder. He simply overdosed on potassium. Luckily for him, his treatment was successful, and he left the hospital three days later, more aware—we can only hope—of the dangers of excess potassium.

While excess-potassium problems are rare in bodybuilders who have normal kidney function, problems of too little potassium are far more common, particularly in those who resort to using potent diuretic drugs in a last-ditch effort to drop excess water prior to a contest. I’ve witnessed dozens of cases over the years of bodybuilders actually passing out backstage because of diuretic abuse. In one celebrated case a pro bodybuilder literally froze during his posing presentation at the Arnold Classic and had to be carried off the stage. He was lucky though; he survived after a short hospital visit. Others haven’t been that lucky and died due to diuretic use. The usual cause of death is heart failure due to electrolyte disturbances brought on by diuretics. One such fatality was pro bodybuilder Mohammed Benaziza, who died during a contest tour in Europe, having used not only massive doses of diuretics but also clenbuterol, a drug that also lowers blood potassium and can interfere with heart function.

In a worst-case scenario having too little potassium can cause your diaphragm to be paralyzed, leading to an inability to breathe. Lack of potassium is also related to rhabdomyolysis, or muscle destruction, which ironically, as mentioned above, leads to excess potassium being released into the blood. You can get low blood potassium from excess vomiting and diarrhea as well. It can also happen due to too high a secretion of aldosterone, severe hyperglycemia—high blood sugar—and certain diuretics. Insulin rapidly lowers blood potassium by pushing it from blood into cells; in fact, insulin is often given to those with elevated blood potassium. Any of the common asthma inhaler drugs also does the same thing.

The same journal that documented the case studies of elevated potassium also discussed the case of an Austrian pro bodybuilder who suffered the consequences of using a potent diuretic called furosemide, or Lasix.2 This particular diuretic promotes a huge excretion of sodium, potassium and magnesium and is well-known for causing painful muscle cramps in bodybuilding competitors. The subject was 26 and was on the usual drug stack of steroids, growth hormone, thyroid and insulin. He claimed that he’d never suffered any adverse side effects from that program, except for an episode of hypoglycemia, or low blood sugar, likely from the insulin. For the first time in his career, however, he’d opted to take two 80-milligram doses of Lasix 24 and 48 hours prior to his contest. He did experience a pronounced diuretic effect, evident by his weight loss of five to six kilograms due to overnight pissing.

The following day, though, he felt unusually tired and decided to take a nap. When he awoke, he felt heart palpitations and couldn’t walk. He got out of bed but immediately fell to the floor. A neighbor saved his life by calling for an ambulance, and he was taken to a local ER. He was treated with several potassium and other mineral drugs to boost his potassium, and he survived. Again, we can only hope that he gained a profound respect for the importance of maintaining potassium levels—as well as the power of diuretics.

If these tales illustrate anything, it’s that you need to be aware of the sources of potassium and the factors that can affect blood levels of it. The second bodybuilder discussed above had no idea that dropping a few potassium pills and drinking over-the-counter sports drinks could land him in the hospital. The prudent way to handle potassium is to get it in food. Supplements are rarely necessary, and many supplements, such as meal substitutes, already contain good amounts of potassium.


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1 John, S.K., et al. (2011). Life threatening hyperkalemia from nutritional supplements: uncommon or undiagnosed? Am J Emerg Med. 29(9):1237.e1-2.

2 Mayr, F.B., et al. (2012). Hypokalemic paralysis in a professional bodybuilder. Am J Emerg Med. 30(7):1324.e5-8.

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